Vent windows pivotally mounted for opening to an angular relation with the main side window plane are well known in the trade as "Fisher no draft" vents.
Power windows having vent elements operating in the same vertical plane as the main window which are first to open and last to close under the operation of power window regulators are also known in the art, as a more recent alternative to the pivoted vent, to provide a relatively small opening for air circulation, venting of cigarette smoke and the like.
Similar manually operable vents vertically slidable in the plane of the main side window having a latch for engaging ratchet teeth to retain the vent window in a raised or adjusted open position have been contemplated which are subject to certain operating deficiencies, particularly in the raised closed position, due to the possibility of the vent window with its latch dropping slightly in reaching a seated position against the ratchet teeth effective to retain the vent window from lowering. Thus, where the fully raised position of the vent window did not exactly match the seated latch position against the ratchet teeth gravity operating on vent window under normal road vibration could cause the vent window to creep downwardly in reaching full latch engagement resulting in air leakage and wind whistle at the top seal.